In 2010, we published the first description of a genetically unique strain of Lassa virus isolated from Mastomys natalensis captured in Mali, an area previously thought to be Lassa virus free (Safronetz et al. 2010). Over the last four years we have continued to conduct field studies mapping the geographic distribution of Lassa virus in peridomestic settings across sub-Saharan Mali. With a better understanding of the regions endemic for this virus in Mali, the Lassa program is transitioning into studies aimed at defining the infection dynamics and transmissibility of Lassa in the natural rodent hosts, as well as defining the incidence rates of Lassa virus infection in humans. The Mali field program has now expanded to include other zoonotic viruses including surveillance for additional arenaviruses, hantaviruses, MERS-CoV, and CCHFV, as well as rodent-specific pathogens including cytomegalovirus.